Last Friday (20/03/2015) central Europe could observe a partial solar eclipse.
Solar eclipse always require, on the astronomers side, big campaigns to tell people how to observe the phenomenon, otherwise they will look directly into it, or worse, point binoculars, cameras and telescopes at it … and get permanently blinded …
The best approach are the campaigns with special goggles, made of a protective film, that cuts 99.999% of the visible light and specially infra-red and ultra-violet light. Of course those goggles are sold out quite quickly, some weeks before the eclipse.
One gets home, the night before the eclipse and there’s a letter from school asking authorization for my kid to go outside and observe the eclipse and asking for the protective glasses, and if possible more than one. Great. How am I going to get something out of business hours that is already sold out for weeks?
With some notice I could have revived the solar projector I did in college for the 1993 solar eclipse back in Brazil and built with the school kids. Simple project: lenses for glasses, pipe to hold and focus the lenses and a mirror to direct the sun light into it.
Too late! So the option was the “shoeboxpinholeinator”!!! (OK, OK, when you have young kids you watch a lot of Disney Channel :-P ) So, the last minute option was to build a shoebox pinhole camera.
Basically get a shoebox, cut an opening on one side, cover it with some aluminium paper and pinhole it. On the other extreme put some white paper, as projection screen. Cut a side opening to be able to see the projection on the white screen, while keeping it mostly in the dark. Close the box, sealing possible light leaks and it’s done.
Me and my son have been experimenting with pinhole cameras recently. As an astronomer and amateur photographer I like a lot the optical part of it and try to bring home some interest in it.
At the end, he took the camera to school (they had collected enough protection goggles anyway) and used it to observe. And me as daddy couldn’t be more proud ;-)